The Big Picture is a photo blog by Alan Taylor, hosted by the newspaper boston.com. The basic idea is the following: Provide a short summary of a current story, and tell it with anywhere between 15 and 45 photos, each with a short description and the source.
Photos are 990px × 667px, which supposedly is too small for prints, but big compared to any other news site. Also photos are just loaded all at once on a single page; you can start looking at the first few while the rest is loading.
The photos themselves aren’t amateur photos taken from Flickr or elsewhere, instead professional photos from various agencies.
For anyone interested in some background information, this interview with Alan Taylor is worth a read.